About this replacement
Retevis RB48 / RB648 — 3.7V Li-Polymer Replacement Battery (BL48 / BL648)
This 3.7V, 2400mAh Li-Polymer battery replaces the original BL48 and BL648 packs in the Retevis RB48 and RB648 handheld two-way radios. It slots into the same battery compartment as the factory pack with no modification. Capacity figure is 2400mAh / 8.88Wh as spec'd by the product data.
- RB48 and RB648 shared platform: Both radios run the same 3.7V single-cell architecture and use an identical battery footprint, connector pitch, and BMS handshake — which is why one pack number (BL48 / BL648) covers both units.
- Bench tested on actual hardware: We cycled the pack through transmit loads on the bench. The BMS held the output rail steady through sustained PTT presses and tripped cleanly at the low-voltage cutoff threshold without locking the pack into a fault state.
- First insertion into the charger dock: If the dock LED flashes a fault pattern on first seating, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The RB48 dock requires a clean contact cycle to complete the BMS handshake before it will begin charging.
Why the RB48 cuts out mid-transmission on a freshly inserted battery
New Li-Polymer cells ship at storage voltage — typically around 3.6–3.75V — not at a full 4.2V charge. When you key up on the RB48, the transmit current spike can pull the cell voltage below the BMS undervoltage threshold momentarily, tripping a cutoff. This is not a fault with the pack. Charge the battery fully in the dock before first use in the field and the transmit rail will stay stable through normal PTT cycles.
Bar indicator showing one fewer bar than expected after installing the BL48
The RB48 uses simple voltage-threshold steps to drive its bar indicator — it does not count capacity. A new pack at storage voltage reads lower on those thresholds than a fully charged cell does, so the radio may show one or two bars even with a fresh battery installed. Run a full charge cycle until the dock LED goes solid green, then power the radio on. The indicator will reflect the correct voltage level at 4.1–4.2V.